Fix/Cleanup: I18N: Bad usage of IFACE_ instead of TIP_.

Cheap tip: anything that is not "Camel Case" and/or that is more than
a few words long should use `TIP_` translation, not `IFACE_` one.

Also added several missing strings (including the one reported in D5056
by Jean First (@robbott), thanks).

source/blender/compositor/intern/COM_ExecutionGroup.cpp

@@ -431,7 +431,7 @@ void ExecutionGroup::finalizeChunkExecution(int chunkNumber, MemoryBuffer **memo
     char buf[128];
     BLI_snprintf(buf,
                  sizeof(buf),
-                 IFACE_("Compositing | Tile %u-%u"),
+                 TIP_("Compositing | Tile %u-%u"),
                  this->m_chunksFinished,
                  this->m_numberOfChunks);
     this->m_bTree->stats_draw(this->m_bTree->sdh, buf);